Stereoscopic image detection devices are known in the art. Such devices are required to obtain and provide a combination of small cross section and high image quality. It will be appreciated by those skilled in the art that high image quality, in general, is characterized by stereoscopic vision accuracy, color capabilities, high resolution and illumination requirements.
It is noted that conventional methods, which provide stereoscopic images, require a wider optical path than a monocular one. Such a widened optical path enlarges the cross-section required for the detection device considerably. Hence, the requirement for a small cross section is not maintained.
U.S. Pat. No. 5,527,263 to Zobel et al., is directed to a dual optical path stereo endoscope with simple optical adjustment. U.S. Pat. No. 5,776,049 to Takahashi, is directed to a “Stereo Endoscope in Stereo Endoscope Imaging Apparatus” and provides a device which utilizes a combination of two optical paths with two CCD units, capable of variable zoom.
Auto-stereoscopic devices, which utilize one optical system to provide a stereo effect, are also known in the art. Such a device is provided in U.S. Pat. No. 5,603,687 to Hori, which is directed to a device with two parallel optical axes and two CCD elements. Hori selected an asymmetrical approach, wherein one optical channel has a large aperture for light and details, and the other optical channel provides a parallax image for stereoscopic imagery to the proximal CCD.
U.S. Pat. No. 5,613,936 to Czarnek, is directed to a stereoscopic endoscope device which utilizes light polarization and time multiplexing, in order to transmit each different polarized image corresponding to left and right images multiplexed in time, through one optical channel that transfers images from the lateral side of the endoscope shaft. This endoscope has to be inserted deeper into the human cavity to receive a stereo image. It must also be used with a head mounted display device called “switched shutter glasses” that causes eye irritation. It is noted that according to Czarnek each image is received in 25% of original quality. As much as 50% of the light received from the object, is lost due to polarization considerations and as much as 50% of the remaining information is lost due to channel switching.
U.S. Pat. No. 5,588,948, to Takahashi et al., is directed to a stereoscopic endoscope. The stereo effect is produced by having a dividing pupil shutter, which splits the optical path onto the left and right sides, and the up and down sides. These sides are alternately projected on a proximal image pick up device, using time multiplexing. According to another aspect of this reference a distal CCD is included, which is divided to left and right sides with a shading member separating them, for achieving space multiplexing.
U.S. Pat. No. 5,743,847 to Nakamura et al., is directed to a “Stereoscopic Endoscope Having Image Transmitting Optical-System and Pupil Dividing Unit that are Axially Movable With Respect to Each Other”, which uses a plural pupil dividing means and one optical channel. U.S. Pat. No. 5,751,341 to Chaleki et al, is directed to a “Stereoscopic Endoscope System”, which is basically a two channel endoscope, with one or two proximal image sensors. A rigid sheath with an angled distal tip could be attached to its edge and be rotated, for full view.
U.S. Pat. No. 5,800,341 to Mckenna et al., is directed to an “Electronically Steerable Endoscope”, which provides different fields of view, without having to move the endoscope, using a plurality of CCD cells and processing means. U.S. Pat. No. 5,825,534 to Strahle, is directed to a “Stereo Endoscope having a Folded Sideline Sight Line” including stereo-endoscope optical channel, having a sight line folded relative to tube axis.
U.S. Pat. No. 5,828,487 to Greening et al., is directed to a “Stereoscopic Viewing System Using a Two Dimensional Lens System” which in general, provides an alternative R-L switching system. This system uses a laterally moving opaque leaf, between the endoscope and the camera, thus using one imaging system. U.S. Pat. No. 5,594,497 to Ahern, describes a distal color CCD, for monocular view in an elongated tube.
The above descriptions provide examples of auto-stereoscopic inventions, using different switching techniques (Time division multiplexing) and polarization of channels or pupil divisions (spatial multiplexing), all in an elongated shaft. When color image pick up devices are used within these systems, the system suffers from reduced resolution, loss of time related information or a widened cross section.
The issue of color imagery or the issue of a shaft-less endoscope is not embedded into any solution.
To offer higher flexibility and to reduce mechanical and optical constraints it is desired to advance the image pick-up device to the frontal part of the endoscope. This allows much higher articulation and tends itself easily to a flexible endoscope. Having a frontal pick up device compromises the resolution of the color device due to size constraints (at this time).
U.S. Pat. No. 5,076,687 to Adelson, is directed to an “Optical Ranging Apparatus” which is, in general a depth measuring device utilizing a lenticular lens and a cluster of pixels.
U.S. Pat. No. 5,760,827 to Faris, is directed to “Pixel Data Processing System and Method for Producing Spectrally-Multiplexed Images of Three-Dimensional Imagery for Use in Stereoscopic Viewing Thereof” and demonstrates the use of multiplexing in color and as such, offers a solution for having a color stereo imagery with one sensor. Nevertheless, such a system requires several sequential passes to be acquired from the object, for creating a stereo color image.
U.S. Pat. No. 5,812,187 to Akira, is directed to an Electronic Endoscope Apparatus. This device provides a multi-color image using a monochromatic detector and a mechanical multi-wavelength-illuminating device. The monochromatic detector detects an image, each time the multi-wavelength-illuminating device produces light at a different wavelength.